Hydrogen storage is important to a wide variety of applications such as fuel cells, portable power generation and hydrogen combustion engines. Typically, hydrogen (H2) is stored in different forms such as in a compressed gaseous form, a liquid form, or a solid-state form. Transportation of high-pressure heavy weight gaseous hydrogen cylinders can have safety issues. Further, liquid hydrogen storage systems may be expensive and may have losses over a period of time due to evaporation or leakage of hydrogen. Additionally, hydrogen leaks can result in safety hazards.
Hydrogen storage in solid-state form can provide safe and efficient storage of hydrogen. Hydrogen can be stored in solid-state materials as physically bound hydrogen molecules or as chemically bound H atoms. A variety of carbon-based materials such as activated carbon, carbon nanofibers, carbon nanotubes (CNTs), and graphene have been explored for hydrogen storage applications. However, such carbon-based materials have relatively low hydrogen storage capacity at ambient temperatures and moderate pressures due to physical adsorption of hydrogen molecules.